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From: Steven Rostedt <rostedt@goodmis.org>
To: "Chuyi Zhou" <zhouchuyi@bytedance.com>
Cc: <tglx@linutronix.de>, <mingo@redhat.com>, <luto@kernel.org>,
	<peterz@infradead.org>, <paulmck@kernel.org>,
	<muchun.song@linux.dev>, <bp@alien8.de>,
	<dave.hansen@linux.intel.com>, <pbonzini@redhat.com>,
	<bigeasy@linutronix.de>, <clrkwllms@kernel.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 02/12] smp: Enable preemption early in smp_call_function_single
Date: Wed, 18 Mar 2026 10:14:42 -0400	[thread overview]
Message-ID: <20260318101442.371c69ae@gandalf.local.home> (raw)
In-Reply-To: <20260318045638.1572777-3-zhouchuyi@bytedance.com>

On Wed, 18 Mar 2026 12:56:28 +0800
"Chuyi Zhou" <zhouchuyi@bytedance.com> wrote:

> diff --git a/kernel/smp.c b/kernel/smp.c
> index fc1f7a964616..b603d4229f95 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -685,11 +685,16 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
>  
>  	err = generic_exec_single(cpu, csd);
>  
> +	/*
> +	 * @csd is stack-allocated when @wait is true. No concurrent access
> +	 * except from the IPI completion path, so we can re-enable preemption
> +	 * early to reduce latency.
> +	 */

Thanks for the comment. I walked through the code and this looks fine to me.

> +	put_cpu();
> +
>  	if (wait)
>  		csd_lock_wait(csd);
>  
> -	put_cpu();
> -
>  	return err;

Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve

  reply	other threads:[~2026-03-18 14:14 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-18  4:56 [PATCH v3 00/12] Allow preemption during IPI completion waiting to improve real-time performance Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 01/12] smp: Disable preemption explicitly in __csd_lock_wait Chuyi Zhou
2026-03-18 14:13   ` Steven Rostedt
2026-03-18  4:56 ` [PATCH v3 02/12] smp: Enable preemption early in smp_call_function_single Chuyi Zhou
2026-03-18 14:14   ` Steven Rostedt [this message]
2026-03-19  2:30     ` Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 03/12] smp: Remove get_cpu from smp_call_function_any Chuyi Zhou
2026-03-18 14:32   ` Steven Rostedt
2026-03-18 15:39     ` Sebastian Andrzej Siewior
2026-03-18  4:56 ` [PATCH v3 04/12] smp: Use on-stack cpumask in smp_call_function_many_cond Chuyi Zhou
2026-03-18 14:38   ` Steven Rostedt
2026-03-18 15:55   ` Sebastian Andrzej Siewior
2026-03-19  3:02     ` Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 05/12] smp: Free call_function_data via RCU in smpcfd_dead_cpu Chuyi Zhou
2026-03-18 16:19   ` Sebastian Andrzej Siewior
2026-03-19  7:48     ` Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 06/12] smp: Enable preemption early in smp_call_function_many_cond Chuyi Zhou
2026-03-18 16:55   ` Sebastian Andrzej Siewior
2026-03-19  3:46     ` Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 07/12] smp: Remove preempt_disable from smp_call_function Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 08/12] smp: Remove preempt_disable from on_each_cpu_cond_mask Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 09/12] scftorture: Remove preempt_disable in scftorture_invoke_one Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 10/12] x86/mm: Move flush_tlb_info back to the stack Chuyi Zhou
2026-03-18 17:21   ` Sebastian Andrzej Siewior
2026-03-18 20:24     ` Nadav Amit
2026-03-18 22:28       ` Nadav Amit
2026-03-19  8:49         ` Sebastian Andrzej Siewior
2026-03-19 10:37           ` Nadav Amit
2026-03-19 10:58             ` Sebastian Andrzej Siewior
2026-03-19 13:41               ` Chuyi Zhou
2026-03-19 14:40                 ` Sebastian Andrzej Siewior
2026-03-20 14:33     ` Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 11/12] x86/mm: Enable preemption during native_flush_tlb_multi Chuyi Zhou
2026-03-18  4:56 ` [PATCH v3 12/12] x86/mm: Enable preemption during flush_tlb_kernel_range Chuyi Zhou

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